A transparent conductive film obtained by laminating a thin film having transparency and a low resistance on a transparent plastic base has been used widely in electric and electronic fields, for example, for applications based on the conductivity, such as transparent electrodes for flat panel displays such as liquid crystal displays and electroluminescent (EL) displays, as well as touch panels.
Along with the spread of personal digital assistants and notebook personal computers with a touch panel, a touch panel more excellent in pen sliding durability than before has recently been required. At the time of inputting with a pen in a touch panel, a transparent conductive thin film in a fixed electrode side and a transparent conductive thin film in a movable electrode (film electrode) side are brought into contact with each other, and it is desired to obtain a transparent conductive film having so excellent pen sliding durability as not to cause damages such as cracks and peeling in the transparent conductive thin film with the pen load at that time.
As means for improving pen sliding durability, there are methods of making a transparent conductive thin film in a movable electrode (film electrode) side crystalline (Patent literatures 1 to 11).
However, conventional transparent conductive films have the following problems.
Patent literatures 1 to 7 disclose transparent conductive films each obtained by forming an under layer produced by hydrolysis of an organic silicon compound on a transparent plastic film base and further forming a crystalline transparent conductive thin film thereon. However, these transparent conductive films are whitened and insufficient in pen sliding durability since their transparent conductive thin films are separated after a linear sliding test carried out at 5.0 N load 300,000 times using a pen made of polyacetal described in a pen sliding durability test described below.
Patent literatures 8 to 11 disclose transparent conductive films wherein crystalline transparent conductive thin films are formed with extremely lowered water in a film formation atmosphere at the time of sputtering. However, to produce these transparent conductive films, a vacuum pump with capability of carrying out vacuum evacuation for a long time or a very high power is needed and thus it is not suitable for industrial applications. Furthermore, the transparent conductive film of Patent literature 11 is whitened and insufficient in pen sliding durability since its transparent conductive thin film is separated after a linear sliding test carried out at 5.0 N load 300,000 times using a pen made of polyacetal described in a pen sliding durability test described below.
Moreover, conventional transparent conductive films each obtained by forming a crystalline transparent conductive thin film are subjected to heat treatment for crystallization, and therefore, the residual strains of the transparent films as bases are moderated to provide transparent conductive films with a low heat shrinkage ratio, and it results in another problem of impossibility of obtaining good flatness by properly shrinking the transparent conductive films by heat treatment when the transparent conductive films are to be used as an upper electrode of a large scale touch panel with a size exceeding 10 inches.